Casino Caraibe (think that is the correct spelling). I haven't been in to gamble but have been to shows there which are quite good. Only visitors (not locals) are allowed into the gambling part and you will need to have your passport with you. I seem to remember that you can only play with foreign currency, not their own dinars. Dress code is fairly relaxed but what we would call 'smart casual', so you are unlikely to need your dinner jacket and bow tie, or a cocktail dress (whichever turns you on), but shorts and sandals would probably not be suitable, nor would a bare chest (for either ladies or gentlemen)
Sorry I can't give you any more info but hope this has helped. All the hotels will be able to tell you more I'm sure.
Have a lovely holiday and don't spend too much in the Casino.